This invention relates to a system and method for detecting, containing and limiting leaks in a system for delivering foam.
Polymeric foams, including polyurethane and polyurea foams, are finding ever increasing use as sealants, fillers and protective coatings. These materials have low thermal conductivities; they are good absorbers of sound and other mechanical vibrations and they are electrically insulating. They exhibit a high degree of adhesion to a variety of substrates and have long-term stability under a wide range of ambient conditions. As a consequence, polymeric foams are of growing use in a variety of manufacturing processes. For example, polymeric foam materials are injected into hollow body cavities in motor vehicles. The foam seals minor cracks and protects welds and other metallic surfaces from corrosion. Additionally, the foam provides a high degree of sound deadening and thermal insulation. Similarly, polymeric foam is sprayed onto floor pans and body panels of the vehicles.
A typical foam delivery system includes sources of foamable materials and a pump to deliver a pressurized flow of the materials. The delivery system further includes a dispenser gun which is in fluid communication with the pump by a length of flexible hose. In many systems, two separate materials are delivered to the dispenser gun by different hoses and are mixed in the gun to generate the foam. In other instances, both materials are delivered to the gun by a single hose. The present invention is applicable to either system.
The hose must have sufficient length to enable the operator to reach the areas where the foam is to be dispensed, without the need for moving the material holding tanks or pump. Additionally, the hose must be flexible and relatively lightweight. In many instances, the hose is externally heated, usually by an electrical resistance heating element. In use, the hose is subjected to mechanical stress by flexing, kinking, and stretching. The effects of such stress are compounded by the fact that the reagents are under pressure, and in most instances are heated to elevated temperatures. As a consequence, it has been found that the hose may sometimes allow leaks.
Leaks present a potential source of pollution and are of particular concern when foam is being used in closed manufacturing plants. Because of the problem of leakage, it has been typically necessary that the application of foams is performed in an enclosed containment booth.
The containment booths typically utilized in the automobile manufacturing industry, have been effectively identical to the complicated booths that have been built for paint spray booths. The air treatment circuitry used with paint spray booths has also been attached to the foam containment booths. For the most part, this air treatment circuitry is not in place to treat vapors or fumes from the spray to fill the vehicle bodies. Rather, the complicated containment booth and gas treatment circuitry have been put used simply for the chance of a leakage of the foam into the environment of the factory. It has been unacceptable to allow such leakage and resultant escape of the foam materials. As such, the containment booths, which typically cost over $1,000,000 to manufacture, have been utilized at each foam spraying station.
Containment booths are not only expensive to construct and operate; they also require dedication of significant manufacturing floor space. Additionally, the very requirement of a containment booth limits the mobility of the process and unduly complicates manufacturing. The requirement is particularly burdensome in the manufacture of motor vehicles, where it may be desirable to inject polymeric foam into a vehicle at a number of separate points along the manufacturing process; to do so would require many additional booths. Additionally, the use of a containment booth becomes more impractical when the foam sealant is being applied to trucks, buses, aircraft, ships and other large vehicles.